LeetCode 110. Balanced Binary Tree

Question

Given a binary tree, determine if it is height-balanced.

For this problem, a height-balanced binary tree is defined as:

a binary tree in which the left and right subtrees of every node differ in height by no more than 1.

https://leetcode.com/problems/balanced-binary-tree/

Solution

• Solution1 – DFS, bottom up

class Solution {
    public boolean isBalanced(TreeNode root) {
        return getHeight(root) != -1;
    }
    
    private int getHeight(TreeNode node) {
        if (node == null)
            return 0;
        int lh = getHeight(node.left), rh = getHeight(node.right);
        if (lh == -1 || rh == -1 || Math.abs(lh - rh) > 1)
            return -1;
        return 1 + Math.max(lh, rh);
    }
}

Complexity:

Time complexity: O(n)

Space complexity: O(n)